Various attempts have been made in the prior art to mount instruments in a stabilized way such that oscillations of the supports for such instruments will not be transmitted to the instruments. For example, U.S. Pat. No. 3,294,467 illustrates a stabilization system for instruments sensitive to low natural oscillating frequencies. The invention described in U.S. Pat. No. 3,294,467 features a spherical container mounted on legs and filled with fluid. A rigid suspension bar extends from inside the top of the sphere to the center of the sphere and a flexible suspension wire extends down from the free end of the suspension bar to support a platform at its center. An instrument is positioned on the platform to one side of the suspension wire's connection point with the platform, and a dummy mass is positioned such that the center of gravity of the volumes supported by the platform coincide with a vertical line through the center of the platform.
U.S. Pat. No. 3,672,743 discloses a similar arrangement to that of U.S. Pat. No. 3,294,467 except for a modification in the contents of the fluid. The fluid material is modified to avoid variations in instrument readings caused by changes in the viscosity of the fluid.
Despite U.S. Pat. No. 3,672,743, instrument errors caused by variations in viscosity still remain a problem for high precision instruments. In addition, the arrangements disclosed in the two patents described above are prone to problems such as inability to control instrument errors due to wobble and rotation of the platform. Moreover, in attempting to achieve stabilization there is sacrificed the freedom of utilizing the platform for other functions such as calibration and dynamic testing of instruments susceptible to vibration noise in the surrounding environment. Still further, the stabilization systems presented in the above two patents are not well suited for use with the very high precision instruments presently available, especially those designed for use in space.
Various other prior art devices have been proposed for providing a stable platform for instruments such as accelerometers. It has been known to suspend platforms by parallel wires, for example, a rectangular platform has been suspended by four cables with one cable connected at each corner, the cables extending vertically from the connection point, such arrangements have not achieved much success A major factor underlying the lack of success for such prior art embodiments is that acceleration reduction is limited by the pendulum equation to the inverse square root of the pendulum height. Damping has also proved difficult, and bounce modes have severely affected performance. Such suspended platforms are also prone to error producing effects such as earth tide, and far field gravity changes as produced by the sun and moon. The parallel wire suspension of a platform is also highly susceptible to errors caused by inadvertent horizontal forces which develop during testing procedures (e.g., input drives) and are directly picked up as lateral acceleration by the instrument positioned on the platform.